Plasma lipoproteins and lipolytic enzyme activities during endurance training in sedentary men: Changes in high-density lipoprotein subfractions and composition

Abstract

Eighteen healthy sedentary males took part in supervised bicycle training for 50 minutes three to five times a week. Twelve subjects (group A) trained for 6 weeks at heavy intensity, and six subjects (group B) trained for 12 weeks at moderate intensity. Maximal oxygen uptake increased by about 20% ( P < 0.01). Body weight and composition as well as diet remained unchanged. After 6 weeks plasma high-density lipoprotein (HDL) cholesterol concentrations had increased by 7% ( P < 0.05) in all subjects. The increase was most marked in group B at 14% ( P < 0.05) compared to 3% in group A (ns). Apolipoprotein AI (apo AI) increased by about 7% in both groups ( P < 0.01). After 12 weeks HDL cholesterol and apo AI levels had almost returned to initial values. Measurements of HDL components showed increases of 6% to 12% in free cholesterol, cholesteryl ester ( P < 0.05), and phospholipid ( P < 0.01); whereas, the minor triglyceride fraction decreased by 20% ( P < 0.01). Zonal ultracentrifugation in four subjects revealed a preferential rise of about 35% in the HDL 2 subfraction, increasing the HDL 2 HDL 3 ratio by about 20%. In parallel, the composition of the lipoprotein classes changed. The protein moiety of all classes, except low-density lipoprotein (LDL), expanded at the expense of the core components cholesteryl ester and triglyceride. Hepatic lipase (HL) activity decreased by 6% ( P < 0.05), and lipoprotein lipase (LPL) activity in adipose tissue increased by about 50% ( P < 0.05) during the first 6 weeks of training, while LPL activity in postheparin plasma and skeletal muscle did not change. The transient rise in HDL cholesterol levels was correlated ( P < 0.05) to the elevation of adipose tissue LPL activity. The alterations in HDL concentration were also related to changes in body composition and diet, especially to an increase in fat intake.